whitehead



TNVENTOH.

Mm, .A a w G. E. WHIT'EHEAD. Screw Tap No.242J73.

WITNESSES,

UNITED STATES PATENT OFFIQE.

THE PROVIDENCE TOOL COMPANY, OF SAME PLACE.

SCREW-TAP.

SPECIFICATION forming part of Letters Patent No. 242,173, dated May 31, 1881.

Application filed March 7, 1881. (No model.)

To all whom it may concern:

Be it known that I, GEORGE E. WHITEHEAD,

of the city and county of Providence,and State l of Rhode Island, have invented anew and useful Improvementin Screw-Taps; and I dohcreby declare that the following specification, taken in connection with the accompanying drawings, forminga part of the same,is atnll,

clear, and exact description thereof.

My invention relates to a tap for producing screw-threads in nuts, 850.; and my improvement consists in a novel construction of the tap, so that its-threaded portion can be expanded andcontracted for the purpose ofpro- 1 ducing a slightly larger or smaller thread.

It is often necessary that the diameter ofthe thread produced by a tap should be slightly varied from a standand size in order that the hole tapped by it may fit a definite screw. It

a is also desirable that a tap should be constructed so that its threaded portion can be expanded when the tap becomes slightly worn, to bring said threaded portion to exact gage. These results I secure by making the threaded portion of thetap adjustable, as will hereinafter appear.

Referring to the drawings, Figurel represents my improved tap in elevation, and Fig. 2 shows the same in longitudinal section.

As shown in both figures of the drawings, the tap is provided with a. slot, A, extending from the shank portion B into the threaded portion B, thereby securing elasticity to the k heel of said threaded portion. For expanding 3 5 the tap ascrew, C,is provided, which is threaded into one-half of the tap and takes bearing againstthe opposite wall of the slotA, as shown in Fig. 2. This screw also prevents the tap For contracting the tap a from springin g.

screw, D, is provided, which is threaded into one half of the tap and has a head bearing in the other half. The action of each screw is opposed to the other. Therefore by proper manipulation the threaded portion of the tap may be expanded or contracted within certain lim- 5 its, and held firmly to the desired gage.

In place ofthe screws C and D, other equiva lent mechanical devices may be substituted to perform the same office, in combination with the longitudinal slot A. 0

I am aware that heretofore reamers have been bit'ureatedthat is, made open-ended, or constructed with two spring-legs which can be contracted or expanded by suitable means-instances ot' the same being shown in United States Letters Patent No. 182,496 and N 0. 225,265. I do not claim, therefore, anything covered by said patents.

For practical use it is necessary that a tap should always start the thread to be out at the same gage, and that any variation in the diameter of its threaded portion should only be at and near thepart which finishes the thread. My improved tap answersthcse requirements, since it-has a solid threaded end, and only that portion of the tap which finishes the thread is adjustable.

HavingdeseribedmyinventiomwhatIelaim, and desire to secure by Letter Patents, is

A solid-ended screw-tap provided with a longitudinal slot, A, and a screw or screws for darying the diameter of the finishing portion thereof and holding the same to a definite gage, substantially as set forth.

GEORGE E. WHITEHEAD.

Witnesses:

W. H. THURSTON, J. KNIGHT. 

